1. Field of the Invention
The present invention relates to an anomalous shadow detection system, and more specifically, to an anomalous shadow detection system which has image output means capable of outputting an improved set of information.
2. Description of the Related Art
Several anomalous shadow detection systems have heretofore been suggested (see, e.g., Japanese Unexamined Patent Publications Nos. 8(1996)-294479 and 8(1996)-287230) to automatically detect those shadows in an image which appear to be anomalous shadows using a computer. The detection is carried out over image data (e.g., medical image data) on an object obtained by an image forming modality such as a CT (computed tomography) apparatus, an MRI (magnetic resonance imaging) apparatus, a CR (computed radiography) apparatus, etc.
Such anomalous shadow detection systems are mainly directed to detection of the anomalous shadow (e.g., a shadow of a tumor or a microcalcification) in a mammography, i.e., the anomalous shadow indicative of breast cancer etc. Each of the anomalous shadow detection systems has anomalous shadow detecting means for automatically detecting those shadows which appear to be anomalous shadows (hereinafter, referred to as “the suspected anomalous shadows”). The anomalous shadow detecting means may utilize an iris filter which extracts as the suspected anomalous shadow a spot in the image where concentration of image density slope vectors (or intensity slope vectors) is high, or a morphology filter which extracts as the suspected anomalous shadow a spot in the image where image density varies within an area smaller than a predetermined structuring element defined in accordance with an estimated size of the anomalous shadow to be detected.
The anomalous shadow detecting means using the iris filter enables automatic detection of a shadow which appears to be the shadow of the tumor (one type of the anomalous shadow hereinafter referred to as “the suspected shadow of the tumor”) indicative of breast cancer etc. On the other hand, the anomalous shadow detecting means using the morphology filter enables automatic detection of a shadow which appears to be the shadow of the microcalcification (another type of the anomalous shadow hereinafter referred to as “the suspected microcalcification shadow”) also indicative of breast cancer etc.
The anomalous shadow detecting means in the anomalous shadow detection system detects the suspected anomalous shadow within the image to be analyzed (i.e., the original image such as a mammograph) inputted to the system. After the detection, ROI defining means defines a local area including the detected suspected anomalous shadow and an adjacent area thereof as a region of interest (hereinafter, referred to as “ROI”). ROI image processing means then processes an image of the ROI in a specialized manner. For example, the ROI image processing means may enhance the ROI image in a predetermined manner defined corresponding to the type of the anomalous shadow to be detected (e.g., the shadow of the tumor or the microcalcification shadow). Concurrently, entire image processing means processes the entire original image in a predetermined manner to improve the readability thereof. Finally, layout image processing means merges the processed ROI image and the processed entire image into a single layout image according to a predetermined layout, and sends information descriptive of the layout image to image display means such as a CRT or printing means such as a laser printer for output.
FIG. 3 shows an example of the layout image L outputted on CRT for the case where a pair of mammographs are used as the original image. In FIG. 3, an entire image P of the right breast and an ROI image W, including a suspected anomalous shadow P1 and an adjacent area P2 thereof, are arranged on the right half of the CRT, and an entire image P′ of the left breast in which no anomalous shadow was detected is shown on the left half of the CRT.
The anomalous shadow detection system detects the suspected anomalous shadow based on a predetermined threshold value for a certain standard parameter. The standard parameter is such a parameter descriptive mainly of a morphological feature etc. of a shadow and may be used to distinguish suspected anomalous shadows from normal shadows. Accordingly, any examiner may pick up the same suspected anomalous shadow regardless of his/her experience in the medical field and level of diagnostic skills.
However, what is detected by the anomalous shadow detection system is nothing more than the suspected anomalous shadow, and whether or not the shadow is a real anomalous shadow must be judged by the examiner (e.g., a doctor) who observes and examines the image outputted on the image display means such as the CRT or the printing means such as the laser printer. Therefore, it is preferable to provide the examiner with some information which supports the judgment in addition to the image itself.